Jody will go to jail if she doesn't pay her ticket, but she may go for some other reason, so 1. Can't be true.
2. Isn't true, either - for the same reason. Jody may go to jail for another offence.
3. Must be true. You know for certain that if Jody doesn't go to jail she must have paid her ticket, because if she hadn't done so she would go to jail.